Conventional geophones employ permanent electric coils suspended and dampened by springs or other means such as air, oil, and the like. The geophone is connected to a pair of wires. Thereafter, an explosion or other geologic moving event is created. The vibrations are picked up by the geophone which causes the coil to move. The movement of the coil in the magnetic field induces a change in voltage which is detected and recorded back at the seismic truck. If the voltage changes are desired in binary form, suitable processing electronics clip the voltage spikes to produce a binary signal. The accuracy of this signal is determined by the stability of the clipping electronics.
When conventional geophones are operated near sources of alternating currents such as high-tension lines, or other sources which produce or use alternating currents, the signals are effected in the 50 Hz to 60 Hz range by the stray electrical sources. Isolation of the geophones from these sources improves results but it is still impossible to eliminate their effect.
Therefore, it would be highly desirable to have a geophone which is not affected by voltage transmission interferences. It would also be desirable to have a geophone which initially produces a binary signal which does not require the use of magnets, coils and clipping electronics.